Antibodies specific for alpha-N-acetyl-beta-endorphins: radioimmunoassays and detection of acetylated beta-endorphins in pituitary extracts

Cannabinoid-induced hyperphagia: correlation with inhibition of proopiomelanocortin neurons?

We tested the hypothesis that cannabinoids modulate feeding in male guinea pigs, and correlated cannabinoid-induced changes in feeding behavior with alterations in glutamatergic synaptic currents impinging upon proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus. Feeding experiments were performed as follows: after a three-day acclimation period, animals were weighed and injected with either the CB1 receptor agonist WIN 55,212-2 (1 mg/kg, s.c.), antagonist AM251 (3 mg/kg, s.c.) or their cremophore/ethanol/saline vehicle (1:1:18; 1 ml/kg, s.c.) each day for seven days. WIN 55,212-2 increased, whereas AM251 decreased, the rate of cumulative food intake. The agonist effect was manifest primarily by increases in meal frequency and the amount of food eaten per meal. By contrast, the antagonist effect was associated with decreases in meal frequency, duration and weight loss. For the electrophysiological experiments, we performed whole-cell patch-clamp recordings from POMC neurons in hypothalamic slices. WIN 55,212-2 decreased the amplitude of evoked, glutamatergic excitatory postsynaptic currents (eEPSCs) and increased the S2:S1 ratio. Conversely, AM251 increased eEPSC amplitude per se, and blocked the inhibitory effects of the agonist. WIN 55,212-2 also decreased miniature EPSC (mEPSC) frequency; whereas AM251 increased mEPSC frequency per se, and again blocked the inhibitory effect of the agonist. A subpopulation of cells exhibited an agonist-induced outward current, which was blocked by AM251, associated with increased conductance and reversed polarity near the Nernst equilibrium potential for K(+). These data demonstrate that cannabinoids regulate appetite in the guinea pig in part through both presynaptic and postsynaptic actions on anorexigenic POMC neurons.

Genetic dissociation of opiate tolerance and physical dependence in delta-opioid receptor-1 and preproenkephalin knock-out mice

Previous experiments have shown that mice lacking a functional delta-opioid receptor (DOR-1) gene do not develop analgesic tolerance to morphine. Here we report that mice lacking a functional gene for the endogenous ligand preproenkephalin (ppENK) show a similar tolerance deficit. In addition, we found that the DOR-1 and ppENK knock-outs as well as the NMDA receptor-deficient 129S6 inbred mouse strain, which also lacks tolerance, exhibit antagonist-induced opioid withdrawal. These data demonstrate that although signaling pathways involving ppENK, DOR, and NMDA receptor are necessary for the expression of morphine tolerance, other pathways independent of these factors can mediate physical dependence. Moreover, these studies illustrate that morphine tolerance can be genetically dissociated from physical dependence, and thus provide a genetic framework to assess more precisely the contribution of various cellular and molecular changes that accompany morphine administration to these processes.

Inflammation-induced changes in primary afferent-evoked release of substance P within trigeminal ganglia in vivo

Substance P (SP) is synthesized in a subset of nociceptive sensory neurons and is released from their peripheral and central terminals. Here we demonstrate with the use of in vivo microdialysis and radioimmunoassay techniques that SP is also released within trigeminal ganglia following intraganglionic application of KCl, veratridine or capsaicin, and after electrical stimulation of peripheral afferent fibers. Both the basal and KCl-evoked release of SP are shown to be dependent on extracellular calcium. Using the turpentine-induced model of unilateral orofacial inflammation we also show that both the basal and KCl-evoked release of SP within trigeminal ganglia are greatly increased on the inflamed side 48 h after induction of inflammation. Coupled with previous demonstrations of excitatory effects of SP on sensory neurons, these results suggest that SP fulfils the role of a non-synaptically released diffusible chemical messenger that may modulate the somatic excitability of neurons within sensory ganglia in inflammatory pain states.

Estrogen modulation of two subpopulations of β-endorphin neurons in ovariectomized guinea pigs distinguished by peripherally injected fluorogold

β-endorphin released by neurons in the arcuate nucleus affects the output of several neuroendocrine systems and estrogen levels modulate the production and secretion of β-endorphin. We used intraperitoneal injection of fluorogold to retrogradely label the cell bodies of neurons that project outside the blood-brain-barrier in conjunction with immunohistochemistry for β-endorphin to dual label the subpopulation of β-endorphin neurons that project to the median eminence or other sites of access to the peripheral circulation. We found that some identified β-endorphin neurons in the arcuate nucleus of ovariectomized guinea pigs sequestered fluorogold. Approximately 7% of β-endorphin-containing cells co-localized with fluorogold. The effect of estrogen on the number of identified β-endorphin cells was examined. A single estradiol benzoate injection to ovariectomized guinea pigs 24 h prior to sacrifice dramatically decreased the total number of β-endorphin cells identified in the rostral, medial and the caudal portions of the arcuate nucleus. Also, a significantly smaller percentage of fluorogold-filled cells was found to contain β-endorphin immunoreactivity in the estrogen-treated group. These data suggest that a subpopulation of β-endorphin neurons has access to the peripheral circulation and may alter the output of neurosecretory terminals at the level of the median eminence. Furthermore, estrogen affects this subpopulation and the general population of β-endorphin neurons in the arcuate nucleus in a similar manner.

N-acetylation and C-terminal proteolysis of beta-endorphin in the anterior lobe of the horse pituitary

beta-Endorphin is post-translationally processed to both N-acetylated and C-terminally shortened derivatives in the anterior lobe of the horse pituitary, a processing pattern qualitatively different from that of the rat and virtually every other mammalian species. Thus, separation of the molecular forms of beta-endorphin using gel filtration and ion exchange chromatography showed that the horse anterior lobe primarily contains beta-endorphin-1-31 and N-acetyl-beta-endorphin-1-27 along with smaller amounts of beta-lipotropin, beta-endorphin-1-27, and N-acetyl-beta-endorphin-1-31 and -1-26, in contrast to the rat anterior lobe, which contains approximately equal amounts of beta-lipotropin and beta-endorphin-1-31. Immunohistochemical experiments using an antiserum which specifically recognizes N-acetylated beta-endorphin peptides confirmed that N-acetyl-beta-endorphin immunoreactivity is present in the anterior lobe of the horse, but not the rat. The intermediate lobe of both species primarily synthesizes N-acetylated, C-terminally shortened beta-endorphin peptides, and while distinct species differences do occur, they were relatively minor, consisting of quantitative differences in the relative proportion of each peptide. These results are consistent with earlier reports that beta-endorphin processing in the rat pituitary is tissue specific; the anterior and intermediate lobes produce entirely different sets of beta-endorphin peptides. In the equine pituitary, however, both pituitary lobes produce the same multiple beta-endorphin forms, possessing both opioid and nonopioid properties, although their relative amounts differ.

Isolation and characterization of opioid peptides from rabbit cerebellum

The rabbit cerebellum has been shown to contain significant quantities of opioid receptors consisting of both mu- and kappa-subtypes. To determine the nature of the endogenous opioid ligands in this tissue, extracts from rabbit cerebellum were separated by various chromatography techniques and fractions were assayed initially for opioid peptides with a radioimmunoassay capable of detecting all peptides with an amino-terminal Tyr-Gly-Gly-Phe sequence. This sequence is common to all mammalian opioid peptides and is critical for recognition by all known opioid receptors. Each of the three immunoreactive opioid peptide peaks detected was purified to homogeneity and subjected to amino acid composition and sequence analysis. One peak was analyzed further by mass spectrometry. This identified the major opioid peptides in the cerebellum as [Met5]enkephalin, [Leu5]enkephalin, and heptapeptide [Met5]enkephalyl-Arg6-Phe7. The comprehensiveness of this initial detection scheme in identifying biologically active opioid peptides was substantiated through subsequent analysis. Using specific radioimmunoassays for representative opioid peptides of the three opioid systems currently known, no other peptides of either the proenkephalin, proopiomelanocortin, or prodynorphin series were detected in any appreciable amounts. Collectively, these results are consistent with the position that rabbit cerebellar opioids are derived from proenkephalin. However, given that no appreciable quantities of either [Met5]enkephalyl-Arg6-Arg7-Val8-NH2 (metorphamide) or [Met5]enkephalyl-Arg6-Gly7-Leu8 were detected suggests that rabbit proenkephalin may have a slightly altered sequence and/or is differentially processed relative to other mammalian species studied.

Developmental expression of proenkephalin mRNA and peptides in rat striatum

The development of proenkephalin (PE) gene expression in the rat striatum was examined at the mRNA and peptide levels. Immunocytochemistry was performed with antisera generated to the PE-specific peptide product Met-enkephalin-Arg-Gly-Leu (MERGL). The distribution of immunostaining was compared with the distribution of PE mRNA, determined by in situ hybridization with an oligonucleotide probe. PE mRNA first appeared at E16 in the caudal ventrolateral striatum, followed at E17-18 by the appearance of MERGL immunoreactivity in a similar distribution. The anatomical gradients of PE gene expression were similar to the pattern of histogenesis of striatal neurons, suggesting that the timing of PE gene expression is related to the time of neuronal withdrawal from the mitotic cycle. The relation of the development of PE gene expression to the known patterns of striatal histogenesis, neurochemical compartmentalization and dopaminergic innervation is discussed.

Differential susceptibility of prevertebral and paravertebral sympathetic ganglia to experimental injury

To investigate the response of selected sympathetic ganglia to experimental injury, neonatal rat pups were treated with either 6-hydroxydopamine (6-OHDA), guanethidine, or antiserum to nerve growth factor (anti-NGF). When examined at one month of age, each of the treatments resulted in a significantly greater loss of neurons and tyrosine hydroxylase activity in paravertebral (superior cervical and stellate) versus prevertebral (superior mesenteric and celiac) sympathetic ganglia. Guanethidine treatment produced the largest differential in neuron loss and tyrosine hydroxylase activity between pre- and paravertebral ganglia. Histologically, the acute phase of guanethidine-induced injury in the superior cervical, paravertebral, ganglia was characterized by a prominent mononuclear cell infiltrate and extensive neuronal degeneration. Minimal histopathologic changes were seen in the superior mesenteric, prevertebral, ganglia of the same animals. Immunolocalization of tyrosine hydroxylase and neuropeptide Y (NPY) in guanethidine-treated animals showed a preferential loss of sympathetic innervation of the extramural mesenteric vasculature with relative sparing of the noradrenergic innervation of Auerbach's myenteric plexus. Differences in the susceptibility of sympathetic ganglia to various insults may underlie the selective and heterogeneous involvement of sympathetic ganglia in clinical and experimental situations.

Post-translational processing of pro-opiomelanocortin (POMC)-derived peptides during fetal monkey pituitary development. II. beta-Lipotropin (beta-LPH)-related peptides

We have studied the post-translational processing of POMC-derived peptides during fetal monkey pituitary development using immunoassay and reverse-phase high-performance liquid chromatography (RP HPLC). Whole pituitary glands obtained from Day 50 and 55 fetal monkeys and separated lobes From Day 65 to 155 were extracted, fractionated, and analyzed for beta-melanotropin (beta-MSH), midportion beta-endorphin (beta-EP), and acetylated beta-EP immunoactivity. Separated adult pituitary lobes were analyzed for comparison. At Day 50, POMC-containing cells were located in both the anterior and intermediate pituitary lobes by immunofluorescence staining, the majority of these cells were localized in the anterior lobe. The Day 50 and 55 whole pituitaries contained predominantly beta-lipotropin (beta-LPH), gamma-lipotropin (gamma-LPH), beta-EP(1-31), and 2.2-kda beta-MSH. No acetylated products were found in Day 50 whole pituitary extracts. By Day 55, carboxy-shortened and acetylated beta-EPs were barely detectable in whole pituitary extracts. These forms were more apparent in the Day 65 separated neurointermediate lobe (NIL) extracts, and were similar to adult proportions by Day 80. The adult anterior lobe contained predominantly beta-LPH, beta-EP, and gamma-LPH. Adult NILs contained almost exclusively 2.2-kda beta-MSH, alpha-N-acetyl beta-EP(1-31) and alpha-N-acetyl beta-EP(1-27). The production of 2.2-kda beta-LPH in the monkey NIL indicates that monkey beta-LPH is different from rat beta-LPH in that it must contain the paired-basic cleavage site required for the formation of 2.2-kda beta-MSH that is known to be lacking in rat beta-LPH. Another finding was that monkey beta-EP contains a Tyr residue at position 27 as found in human beta-EP but appears to have the rat Gln substitution at position 31. The post-translational processing patterns characteristic of each lobe were well established by midterm fetal development (Day 80).

Human beta-casomorphin-8 immunoreactive material in the plasma of women during pregnancy and after delivery

A method for the extraction of human beta-casomorphin-8 immunoreactive material from human plasma and a radioimmunoassay for its determination in the plasma extracts were developed. Blood was collected from 34 men, from 35 non-pregnant women, from 35 pregnant women and from 138 women after delivery and plasma extracts were assayed for the presence of human beta-casomorphin-8 immunoreactive materials. No human beta-casomorphin-8 immunoreactive material was detected in the plasma of men or non-pregnant women, whereas such material was found in the plasma of 26 out of 35 pregnant women and in the plasma of 100 out of 138 women after parturition. Material collected from women after delivery was characterized by gel filtration and high-performance liquid chromatography (HPLC) and was found to be of different composition in various individuals; its components, one of which coeluted with human beta-casein from the HPLC column, have apparently higher molecular weights than human beta-casomorphin-8. Some of these compounds seem to be very stable against enzymatic degradation at 37 degrees C in human plasma, whereas human beta-casomorphin-8 proved to be degraded very fast under identical conditions. A physiological significance of mammary products of the beta-casomorphin type during pregnancy or after parturition is suggested.

Basic fibroblast growth factor: expression in cultured cells derived from corneal endothelium and lens epithelium

We have examined the possible expression of fibroblast growth factor in cultured cells derived from bovine lens epithelium and corneal endothelium. Lens epithelial, but not corneal endothelial, cells were found to express the acidic fibroblast growth factor (aFGF) gene, whereas both cell types express the gene encoding basic fibroblast growth factor (bFGF), a related mitogen. Expression of bFGF was further examined. Both corneal endothelial and lens epithelial contain 3.7 and 7.0 k bFGF gene transcript, which are translated into material closely related, if not identical with bFGF. Essentially all of the bFGF-like material is bioactive, i.e. it can stimulate the proliferation of capillary endothelial or corneal endothelial cells and the stimulation is blocked by anti-bFGF antibodies. Our results indicate that bFGF derived from corneal endothelial and lens epithelial cells may act as a paracrine and autocrine growth factor in both cell types. Thus, bFGF present in both cell types may play an important role in the proliferation of injured or transformed ocular tissues.

Expression of opioid peptides in tumors

We looked for opioid peptides and their precursors in 108 tumors of both neuroendocrine and nonneuroendocrine origin, using a monoclonal "pan-opioid" antibody, 3-E7, which recognizes the tetrapeptide Tyr-Gly-Gly-Phe (the sequence responsible for pharmacologic activity in all known opioid peptides), in conjunction with polyclonal antibodies directed against representative peptides of each of the three precursors (alpha-endorphin, [met]enkephalin-Arg-Gly-Leu, and dynorphin B). Using the avidin-biotin immunoperoxidase technique, we observed consistent cytoplasmic immunoreactivity (at least focally) in all of 15 adrenal pheochromocytomas, all of 6 thyroid medullary carcinomas, and all of 5 pituitary adenomas. Opioid staining was also observed in parathyroid adenomas (8 of 9), pancreatic islet-cell tumors (7 of 10), carcinoid tumors from various sites (18 of 26), and paragangliomas (1 of 2). There was no immunoreactivity in pulmonary small-cell carcinomas, Merkel-cell tumors of skin, neuroblastomas, or any of the non-neuroendocrine tumors examined. The expression of alpha-endorphin, [met]enkephalin-Arg-Gly-Leu, and dynorphin B varied from tumor to tumor; however, positive staining with the "pan-opioid" antibody was found in each tumor containing at least one of the three precursors. Opioid peptide immunoreactivity was also detected in non-neoplastic cells of the adrenal medulla, pancreatic islets, pituitary, intestinal and bronchial mucosa, and intestinal myenteric plexuses. We conclude that opioid expression within tumors is most likely due to enhanced expression of a normal cell product and that opioid peptides are useful markers of neuroendocrine differentiation in many tumors.

Isolation and characterization of beta-endorphin-(1-9) from human and rat pituitaries

Using a radioimmunoassay specific for the carboxyl terminus of beta-endorphin-(1-9) large amounts of beta-endorphin-(1-9)-immunoreactive material was detected in the human pituitary. The major peak of immunoreactivity was purified and characterized by fast atom bombardment-mass spectrometry and Edman degradation sequencing as authentic beta-endorphin-(1-9). In the rat pituitary the highest concentration of beta-endorphin-(1-9) immunoreactivity was in the posterior neurointermediate lobe. This material was identified as N-acetyl beta-endorphin-(1-9) by multiple radioimmunoassays, gel chromatography, and reversed-phase high-performance liquid chromatography. Control experiments determined that beta-endorphin-(1-9) was not formed postmortem or during the extraction procedure. These studies suggest that single lysine residues, similar to single arginine residues, are potential sites of posttranslational processing.

Peptide E and its products, BAM 18 and Leu-enkephalin, in bovine adrenal medulla and cultured chromaffin cells: release in response to stimulation

Peptide E is a 25 amino acid opioid peptide which, if cleaved at the sole double basic (Lys-Arg) typical processing site, would generate two opioid fragments, the amino-terminal fragment BAM 18 and the carboxy-terminal fragment Leu-enkephalin. We have analysed extracts of bovine adrenal medulla in order to quantify these three opioid peptides (peptide E, BAM 18, and Leu-enkephalin). Here we present evidence that BAM 18 and Leu-enkephalin were present in similar amounts, whereas peptide E was present at a higher concentration. This is consistent with previous observations showing a preferential accumulation of larger peptides in the bovine adrenal, and also with the Lys-Arg bond being the principal site of cleavage of peptide E. However, when bovine adrenal chromaffin cells were maintained in culture for several days, Leu-enkephalin was found to be present in much greater amounts than was BAM 18-like immunoreactivity. The molar amounts of peptide E still exceeded the estimated levels of BAM 18 and Leu-enkephalin. We provide evidence that under conditions of basal release BAM 18 and peptide E were released, whereas Leu-enkephalin was released in much smaller amounts, if at all. On stimulation with nicotine results were consistent with an increased release of all three peptides with a preferential stimulation of Leu-enkephalin release. Under all conditions, the molar amounts of peptide E released apparently exceeded that of the other peptides. The results are discussed in terms of the regulation of partial proteolysis and the fate of peptide E.

N-acetylated endorphins in ovine anterior pituitary and neuro-intermediate lobe

We have used an antiserum for immunohistochemistry and RIA/RP-HPLC which recognizes all fragments of N-acetylated endorphin (NacEP). In the rat neuro-intermediate lobe (N-IL), in addition to the N-acetylated forms of immunoreactive-beta-endorphin (ir-beta EP) already reported, we have demonstrated Nac beta EP as a minor component. In the sheep pituitary processing of beta EP is markedly different. In the anterior pituitary (AP), staining was indistinguishable with beta EP and NacEP antisera, in contrast with the rat where many fewer AP cells stained with the NacEP antiserum. Secondly, as in the rat, all N-IL cells stained with both antisera; on RP-HPLC, however, the major forms of NacEP in the sheep N-IL were Nac beta EP (approximately 40%), Nac beta EP (approximately 25%) and Nac beta EP (approximately 20%), with Nac beta EP (approximately 2%) as a minor component. A similar profile was seen on RP-HPLC of sheep AP. These data suggest that (1) patterns of processing in sheep AP are similar to those in N-IL, though the extent of acetylation is less and (2) in the sheep pituitary low molecular weight acetylated fragments predominate, in contrast with the rat.

Basic fibroblast growth factor as a growth inhibitor for cultured human tumor cells

Basic fibroblast growth factor (bFGF) stimulates the proliferation of many cells and it is found in a wide variety of normal or transformed tissues. As demonstrated here, bFGF is also present in cultured human Ewing's sarcoma cells. Unexpectedly, however, bFGF isolated from these cells inhibits their own proliferation, indicating that bFGF can act as an endogenous (autocrine) growth inhibitor for cultured Ewing's sarcoma cells. Since bFGF also inhibits the proliferation of some further tumor cells, but stimulates that of others, it can be considered a bifunctional regulator of tumor cell proliferation. The autocrine growth-inhibitory effect of bFGF in Ewing's sarcoma cells may explain the low mitotic activity of Ewing's sarcomas.

Distribution pattern of metorphamide compared with other opioid peptides from proenkephalin and prodynorphin in the bovine brain

Metorphamide is a [Met]-enkephalin-containing opioid octapeptide with a C-terminal alpha-amide group. It is derived from proenkephalin and is, so far, the only endogenous opioid peptide with a particularly high affinity for mu opioid (morphine) receptors, a somewhat lesser affinity for kappa opioid receptors, and a relatively low affinity for delta opioid receptors. The concentrations of metorphamide in the bovine caudate nucleus, the hypothalamus, the spinal cord, and the neurointermediate pituitary were determined by radioimmunoassay and chromatography separation procedures. Metorphamide concentrations were compared with the concentrations of eight other opioid peptides from proenkephalin and prodynorphin in identical extracts. The other opioid peptides were [Met]-enkephalyl-Arg6-Phe7 and [Met]-enkephalyl-Arg6-Gly7-Leu8 from proenkephalin; alpha-neoendorphin, beta-neoendorphin, dynorphin A(1-8), dynorphin A(1-17), and dynorphin B from prodynorphin; and [Leu]-enkephalin, which can be derived from either precursor. All opioid peptides were present in all four bovine neural tissues investigated. Metorphamide concentrations were lower than the concentrations of the other proenkephalin-derived opioid peptides. They were, however, similar to the concentrations of the prodynorphin-derived opioid peptides in the same tissues. Marked differences in the relative ratios of the opioids derived from prodynorphin across brain regions were observed, a finding suggesting differential posttranslational processing. Differences in the ratios of the proenkephalin-derived opioids across brain regions were less pronounced. The results from this study together with previous findings on metorphamide's mu opioid receptor binding and bioactivities suggest that the amounts of metorphamide in the bovine brain are sufficient to make this peptide a candidate for a physiologically significant endogenous mu opioid receptor ligand.

Characterization of opioid peptides in human thyroid medullary carcinoma

A thyroid medullary carcinoma from a man with the multiple endocrine neoplasia syndrome Type IIB was examined for the presence of opioid peptides. The tumor contained peptides derived from all three opioid precursors: pro-opiomelanocortin (POMC), pro-dynorphin, and pro-enkephalin. The tissue concentrations of the various opioid peptides varied considerably. beta-Endorphin, a POMC-derived peptide, was present in concentrations between 9 to 12 pmoles/g tissue; 8 pmoles/g tissue of alpha-neo-endorphin, a pro-dynorphin-derived product, were seen, whereas the pro-enkephalin-associated peptides were present in much lower concentrations (0.6-2.1 pmoles/g tissue). Immunohistochemical studies showed scattered opioid-positive cells in the tumor tissue and in two other thyroid medullary carcinomas. These data demonstrate that malignant neuroendocrine tumors may contain peptides derived from all three families of the endogenous opioids.

Isolation of enzyme cDNA clones by enzyme immunodetection assay: isolation of a peptide acetyltransferase

The biological activity of many proteins and peptides can be profoundly affected by enzyme-catalyzed covalent modifications such as acetylation, sulfation, glycosylation, or amidation. This article describes the cloning of such an enzyme, a peptide acetyltransferase from rat brain that catalyzes the amino-terminal acetylation of endorphins and perhaps other substrates in vivo. Blot-hybridization analysis suggests that the mRNA encoding the acetyltransferase is approximately 2.0 kilobases, is present in whole rat brain and rat hypothalamus, and is slightly larger in mouse AtT20 tumor cells. The acetyltransferase was cloned by using a strategy whereby a cDNA expression library was screened with a solid-phase enzyme-activity assay; this technique combines the use of the substrate coupled to a solid support and subsequent recognition of the product by using a specific antiserum. We have called this method the enzyme immunodetection assay (EIDA). The EIDA should prove useful in the isolation of other clones for proteins that possess enzymatic activity upon expression in bacterial hosts.

Capillary endothelial cells express basic fibroblast growth factor, a mitogen that promotes their own growth

Angiogenesis, the formation of new capillaries, which is observed in embryonic and injured tissue and is particularly prominent in the vicinity of solid tumours, involves the migration and proliferation of capillary endothelial cells. It is probably triggered by agents, such as basic fibroblast growth factor (bFGF), thought to be released from tissues adjacent to proliferating capillaries. As well as being a potent inducer of cell division in capillary endothelial cells in vitro, bFGF can act as an angiogenic agent in vivo. It is present in a wide variety of richly vascularized tissues including brain, pituitary, retina, adrenal gland, kidney, corpus luteum, placenta and various tumours. So far, however, the normal bFGF-producing cell species in these tissues have not been identified. We report here that capillary endothelial cells express the bFGF gene, that they produce and release bFGF and that bFGF derived from them can stimulate the proliferation of capillary endothelial cells. We conclude that bFGF can act as a self-stimulating growth factor for capillary endothelial cells, and that it is possible that the formation of new capillaries is induced by capillary endothelial cells themselves.

Inbred strains of mice with variable sensitivity to ethanol exhibit differences in the content and processing of beta-endorphin

The content of beta-endorphin-like immunoreactivity (beta-EPLIR) in the anterior and neurointermediate lobe of the pituitary gland, the hypothalamus and the serum of the c57BL/6, BALB/C and DBA/2 inbred strains of mice was estimated at the resting state as well as 45 min after i.p. injection of either ethanol solution (3.0 g/kg.b.wt.) or saline. At the resting state, the neurointermediate lobe and the serum of the c57BL/6 mice showed the highest content of beta-EPLIR, while no statistically significant difference was noticed in the total beta-EPLIR content in the anterior lobe and hypothalamus. At 45 min post-ethanol treatment the beta-EPLIR content was increased in the serum of all three strains of mice studied and was decreased in the hypothalamus of the c57BL/6 mice only. Further analysis of the beta-endorphin peptides using sephadex G-75 chromatography and reverse phase high performance liquid chromatography indicated strain differences in the relative proportions of the various forms of beta-endorphin in the anterior lobe, neurointermediate lobe and the hypothalamus. These strain specific differences in the content and post-translational processing of beta-endorphin may be involved in some of the genetically determined differences in responses to ethanol by these inbred strains of mice.

Determination of β-Endorphin and Fragments Thereof in Human Plasma Using High-Performance Liquid Chromatography and a Multiple Radioimmunoassay System

A method for the determination of β-endorphin and β-endorphin fragments in human plasma was developed. β-Endorphin-related peptides were extracted from plasma using octadecasilyl-silica cartridges. Extracts were subjected to re versed-phase high-performance liquid chromatography (HPLC). Extracts as well as HPLC column eluates were assayed using a multiple radioimmunoassay system; several antibodies directed against various distinct regions of the β-endorphin molecule were employed. Using this method, evidence for the presence of multiple β-endorphin fragments in the plasma of healthy young volunteers (under normal conditions) was obtained.

Small cell carcinoma cell lines contain opioid peptides and receptors

Two human small cell carcinoma cell lines were assayed for total opioid and beta-endorphin-like immunoreactivity. Small cell carcinoma cell line NCI-H146 contained approximately 1.1 pmol/mg protein of total opioid immunoreactivity. This material was similar in size and immunoreactive determinants to C-terminally modified beta-endorphin. Small cell carcinoma cell line NCI-H187 contained approximately 0.2 pmol/mg protein total opioid immunoreactivity, which was of low molecular weight. NCI-H187 also contained approximately 1.2 pmol/mg protein of material similar in size and immunoreactive determinants to beta-lipotropin. The two small cell carcinoma cell lines were also examined for opioid receptors with the use of [3H]-etorphine as ligand. Both cell lines contained between 50 and 100 fmol/mg protein of specific, saturable, high-affinity opioid receptor binding sites. Together, these findings suggest a possible autocrine role for opioids in small cell carcinoma of the lung.

Characterization of endorphins from the pituitary of the spiny dogfish Squalus acanthias

Opioid-like immunoreactive material was extracted from the pituitary and brain of the Spiny Dogfish Shark Squalus acanthias. The immunoreactive material in the pituitary extracts was purified to apparent homogeneity by reverse phase high performance liquid chromatography and subsequently characterized by amino acid analysis, Edman degradation and fast atom bombardment mass spectrometry. The largest opioid-like peptide isolated contained 30 amino acids and showed 80 percent homology with salmon endorphin-II but less than 50 percent homology with human beta-endorphin. Three structural variants of this molecule were also characterized. These variants were shown to be shorter N-terminal fragments, two of which corresponded to cleavage products at the single basic residues arginine and lysine. Cleavage at a single lysine residue has not been reported for posttranslational processing of beta-endorphin in mammals and could represent a modification seen only in lower vertebrates. The remaining fragment corresponded to a loss of 3 residues from the C-terminus of the parent molecule. No alpha-N-acetylated peptides were detected. These results provide the first unequivocal confirmation of beta-endorphin in an elasmobranch and provide evidence of novel N-terminal variants of beta-endorphin.

Isolation and characterization of substance P, substance P 5-11, and substance K from two metastatic ileal carcinoids

Using an antiserum directed at the COOH-terminus of tachykinins, we have examined postmortem tissue from two cases of metastatic ileal carcinoid for the presence of tachykinin-like immunoreactivity. The vast majority of the immunoreactive tachykinin-like material eluted from a Sephadex G-50 column as two peaks at positions corresponding to molecular weights of 1300 and 850. The 1300 dalton peak was resolved by reverse-phase-HPLC into two components which by Edman sequencing, amino acid analysis, and fast atom bombardment (FAB)-mass spectrometry criteria, were identified as substance P and substance K. The 850 dalton peak was also resolved on RP-HPLC into two peaks which were resistant to Edman degradation but from amino acid analysis and FAB-mass spectrometry criteria were identified as pyro-Glu-substance P 5-11 and oxidized pyro-Glu-substance P 5-11. In control experiments substance P 5-11 was converted to pyro-Glu-substance P 5-11 during the extraction procedure. Both tumors also contained a minor immunoreactive peak which eluted from a Sephadex G-50 sizing column at a position corresponding to a molecular weight of 4000 which probably represents neuropeptide K. These results suggest that beta-preprotachykinin is preferentially expressed in carcinoid tumors and that substance K may also play a role in the carcinoid syndrome.

Changes in the processing of beta-endorphin in the hypothalamus and pituitary gland of female rats during sexual maturation

Puberty in the female rat is accompanied by a marked attenuation of the opioid inhibition of luteinizing hormone secretion. One factor which may contribute to this altered role is a change in the metabolism of opioid peptides during sexual maturation. beta-Endorphin undergoes a considerable degree of metabolism through both C-terminal proteolysis and N-acetylation, and these metabolites do not possess opioid activity. The processing of beta-endorphin in the hypothalamus and in the anterior and neurointermediate lobes of the pituitary gland in prepubertal and adult female rats was studied using gel filtration and high performance liquid chromatography coupled with radioimmunoassay. In the anterior lobe, high molecular weight precursors of beta-endorphin (pro-opiomelanocortin and beta-lipotropin) were present in prepubertal (28 days old) rats, but little authentic beta-endorphin was detected. In contrast, only beta-lipotropin and beta-endorphin were present in mature (70 days old) animals. Only beta-endorphin-sized peptides were present in the neurointermediate lobes of both prepubertal and adult rats. However, the proportion of N-acetylated metabolites was higher in sexually mature animals. In the hypothalamus, only beta-endorphin-sized peptides were present in both juvenile and adult animals. However, C-terminal proteolysis increased with age (no acetylated metabolites were detectable in this tissue). The proportion of the total beta-endorphin-like immunoreactivity attributable to beta-endorphin was lower in young adult (first dioestrus after vaginal opening) (55%) and mature (dioestrus, 61-64 days old) rats (56%) compared to prepubertal (30 days old) animals (75%) and the proportions of non-acetylated metabolites [beta-endorphin-(1-27) in young adults and beta-endorphin-(1-26) in adults] were increased concomitantly. These changes were correlated with a reduced luteinizing hormone response to the opiate antagonist naloxone in adult compared to prepubertal rats. beta-Endorphin is processed differently in the two lobes of the pituitary gland and in the hypothalamus and the degree of metabolism increases as the rat reaches sexual maturity. The increased metabolism of beta-endorphin in the hypothalamus, the site most likely to be involved in the control of luteinizing hormone secretion, results in a reduction in the relative proportion of the opioid active parent peptide. Thus, increased inactivation of beta-endorphin may contribute to the attenuation of the opioid inhibition of luteinizing hormone secretion observed during puberty.

Effects of dehydration on pro-dynorphin derived peptides in the neuro-intermediate lobe of the rat pituitary

Dehydration significantly reduced the concentration of immunoreactive dynorphin A(1-17), dynorphin A(1-8), alpha-neo-endorphin, beta-neo-endorphin, and leu-enkephalin in the rat pituitary posterior-intermediate lobe. A statistically significant increase in immunoreactive dynorphin A(1-8), alpha-neo-endorphin and leu-enkephalin was observed in the hypothalamus. Comparison of the molar ratios of dynorphin A(1-17): dynorphin A(1-8) and alpha-neo-endorphin: beta-neo-endorphin showed an altered profile of stored pro-dynorphin cleavage products in the posterior-intermediate lobe of the pituitary of dehydrated rats.

The identification and characterization of alpha-N-acetylated beta-endorphin in the human pituitary gland

By using a radioimmunoassay specific for alpha-N-acetyl beta-endorphin and its C-terminally shortened forms, we have established the presence of immunoreactive alpha-N-acetyl endorphin (irNacEP) in extracts of five postmortem human pituitary glands (2.27 +/- 0.64 ng/gland). This immunoreactivity has been further characterized by subjecting these extracts to reverse-phase high-performance liquid chromatography (RP-HPLC). In all cases the major peaks of irNacEP co-migrated with synthetic human standard alpha-N-acetyl alpha-endorphin (Nac alpha EP), alpha-N-acetyl gamma-endorphin (Nac gamma EP) and Nac beta EP. These studies thus represent the initial demonstration that alpha-N-acetylation of beta-endorphin and its shorter molecular forms occurs in the human pituitary gland.

Effects of chronic ethanol treatment on the in vitro biosynthesis of pro-opiomelanocortin and its posttranslational processing to beta-endorphin in the intermediate lobe of the rat pituitary

Chronic treatment of rats with 15% (vol/vol) ethanol in tap water as their only source of liquid over a period of 3 weeks resulted in a strong decrease by almost 50% in tissue levels and in vitro release of immunoreactive beta-endorphin of the neurointermediate pituitary. Moreover, the in vitro incorporation of [3H]phenylalanine into peptides of the neurointermediate pituitary, immunoprecipitable with beta-endorphin antiserum, was found to be decreased by more than 30%. Analysis of beta-endorphin-related peptides on sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that chronic ethanol treatment reduced the in vitro biosynthesis of the beta-endorphin precursor pro-opiomelanocortin. This ethanol-induced effect was combined with a retardation in the time course of the posttranslational processing of the precursor into beta-endorphin. Thus, chronic ethanol treatment may influence the activity of enzymes which process the opioid peptide precursor pro-opiomelanocortin, leading to a decreased formation of the final secretory product beta-endorphin.

Regional distribution of metorphamide in rat and guinea pig brain

A specific radioimmunoassay was developed for metorphamide, an endogenous, amidated opioid octapeptide, originally isolated from bovine brain and human pheochromocytoma tissues. The radioimmunoassay was used to determine the concentration of immunoreactive metorphamide in extracts from dissected regions of rat and guinea pig brain. Radioimmunoassay interfacing with Sephadex gel filtration and reverse phase high performance liquid chromatography confirmed that the immunoreactive substance measured corresponded to authentic metorphamide. Metorphamide was found to be widely distributed in brain regions from both species. However, the concentrations of immunoreactive metorphamide in regions from guinea pig brain were up to 5 times higher than the concentrations of immunoreactive metorphamide in rat brain regions. The results suggest that metorphamide is a specific processing product from proenkephalin in rodent brain.

Distribution and characterization of synenkephalin immunoreactivity in the bovine brain and pituitary

The distribution of synenkephalin, the N-terminal fragment of proenkephalin, was studied in various parts of the bovine brain (globus pallidus, caudate nucleus, hypothalamus) and in the posterior pituitary by the use of a radioimmunoassay. The distribution of synenkephalin-immunoreactivity (IR) was compared to the distribution of Met-enkephalin-IR. Gel exclusion chromatography was used to examine the molecular forms of the immunoreactivities present in the tissues. The distribution of synenkephalin-IR was similar to the distribution of Met-enkephalin-IR, with a molar ratio of Met-enkephalin/synenkephalin ranging between 2.7 and 5.9. In all regions tested except the hypothalamus the synenkephalin-IR was present as a single species. However, in the hypothalamus a small amount of IR material (3% of the total synenkephalin-IR) was detected in fractions where larger Met-enkephalin-containing peptides eluted. Based on the concordance between the molar ratio of Met-enkephalin to synenkephalin found in the tissues and the molar ratio present in the sequence of adrenal proenkephalin, it is concluded that the brain and adrenal glands utilize a similar precursor for enkephalin biosynthesis.

Metorphamide: isolation, structure, and biologic activity of an amidated opioid octapeptide from bovine brain

Acid acetone extracts of caudate nucleus from bovine brain were found to contain an amidated opioid octapeptide with the following structure: Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-NH2. The peptide has been named metorphamide. Bovine metorphamide appears to be derived by proteolytic cleavage from proenkephalin, the common precursor to [Met5]enkephalin and [Leu5]enkephalin. The cleavage within the precursor giving rise to the carboxyl terminus of metorphamide occurs at a single arginine residue and is followed by transformation of a carboxyl-terminal glycine into an amide group. Metorphamide was detected in bovine caudate nucleus extracts by radioimmunoassay, and it was purified to homogeneity by gel filtration and reversed-phase high performance liquid chromatography. Amino acid composition analysis and automated Edman degradation in the gas-phase sequencer confirmed the postulated amino acid sequence. Carboxyl-terminal amidation of bovine metorphamide was shown by stability to carboxypeptidase A digestion and full crossreactivity in a radioimmunoassay that required the carboxyl-terminal amide as part of the recognition site. A synthetic replicate of metorphamide as well as several synthetic analogs were tested for opioid activity in several bioassays and binding assays, and metorphamide was found to have a high mu-binding activity. Metorphamide is the only known naturally occurring opioid peptide that has a high mu-binding activity. The kappa-binding activity is approximately equal to 50% that of the mu-binding activity, but delta-binding activity is negligible.

Identification of pro-opiomelanocortin-derived peptides in the human adrenal medulla

Extracts from adult human adrenals contained high concentrations of immunoreactive beta-endorphin and alpha-melanotropin. Lower quantities of immunoreactive adrenocorticotropic hormone could also be detected. Distribution studies showed the presence of pro-opiomelanocortin fragments in the adrenal medulla. No alpha-melanotropin, beta-endorphin, or adrenocorticotropic hormone could be found in adrenal extracts from several other mammalian species. Analysis of the beta-endorphin-like immunoreactivity using region specific radioimmunoassays interfacing with gel filtration and reverse-phase high-performance liquid chromatography showed the majority of the beta-endorphin-like material to exist as nonacetylated beta-endorphin-(1-31) with a small percentage of lipotropin-sized molecules. The alpha-melanotropin-like immunoreactivity cochromatographed on gel filtration and reverse-phase high-performance liquid chromatography with desacetyl alpha-melanotropin. The data suggest that pro-opiomelanocortin is expressed in the adrenal medulla of humans but is not detectable in the adrenal glands of many other mammalian species.

The effect of naloxone on vasopressin release from rat neurohypophysis incubated in vitro

Rat posterior pituitaries were superfused in vitro and stimulated electrically. The concentrations of vasopressin in the superfusion medium were determined by radioimmunoassay. When the pulses were applied in 10 sec trains with 10 sec intervals, vasopressin release per pulse increased progressively over the frequency range of 3-12 pulses/sec applied within the trains. The release was blocked by addition of tetrodotoxin or by removal of calcium ions from the superfusion medium. The opiate antagonist naloxone 1 or 10 microM was introduced into the superfusion medium before a second period of stimulation and enhanced vasopressin release from neurointermediate lobes after phasic stimulation at 9 pulses/sec within the trains, when compared to controls. However, naloxone 10 microM had not effect on vasopressin release from isolated neural lobes (intermediate lobes removed), although the addition of camel beta-endorphin 2 microM inhibited vasopressin release in a naloxone-reversible manner. After continuous stimulation at a frequency of 13 Hz naloxone 10 microM did not influence the release of vasopressin from neurointermediate lobes. We conclude that the evoked release of vasopressin from the neurointermediate lobe is reduced by an endogenous opiate of intermediate lobe origin, possibly beta-endorphin. Appropriate stimulation conditions are necessary for this mechanism to function.

Monoclonal antibody to the message sequence Tyr-Gly-Gly-Phe of opioid peptides exhibits the specificity requirements of mammalian opioid receptors

Six myeloma cell hybrids producing antibodies to human beta-endorphin were isolated from a single mouse spleen. The monoclonal antibodies displayed different binding patterns with the antigen. We report the characterization of one antibody which recognizes the tetrapeptide Tyr-Gly-Gly-Phe representing the message sequence found at the NH2 terminus of all naturally occurring mammalian opioid peptides. Competition experiments in radioimmunoassay and immunohistochemistry show that the antibody fails to bind the beta-endorphin precursor beta-lipotrophin, does not discriminate among opioid peptides that share the same message sequence but have different COOH-terminal extensions, and does not react with pharmacologically inactive derivatives of beta-endorphin. The antibody recognition of the message sequence of natural opioid peptides is sensitive to those molecular changes that affect their receptor binding competence.

Observations on N alpha-deacetylation of model amino acids and peptides: distribution and purification of a specific N-acyl amino acid releasing enzyme in rat brain

N alpha-Acyl amino acid releasing enzyme (NAARE), an enzyme cleaving acetylMet-Ala at the Met-Ala bond was purified from rat brain cytosol to apparent homogeneity by salt precipitation, gel filtration, and several steps of ion exchange. Levels of NAARE exceeded acylase measured with acetylmethionine in all brain regions and subcellular fractions examined: 60% was associated with cytosol and the remainder with debris or the crude nuclear and mitochondrial-synaptosomal subfractions. Activity was highest in pituitary and was approximately 0.5-0.6 that of liver or kidney. The purified enzyme preferentially hydrolyzed acetylmethionyl peptides: Km for acetylMet-Ala was 0.93; Vmax, 3.5 nmol-1 (kcat, 1185) with pH optimum of 8.9 as compared with 8.2 for acylases measured in cytosol. The purified enzyme was devoid of acylase and common exo- and endopeptidase contamination. Structure-activity relationships examined with synthetic formylated or acetylated peptides indicated no significant effects for di- or tripeptides if the second substituent was Ala, Ser, Asn, or Thr, but the activity was reduced 0.5-fold for Leu, a branched-chain amino acid. No hydrolysis was observed for polypeptides with five or more residues having N-terminal acetylated Tyr (enkephalin) or Ser (alpha-melanocyte-stimulating hormone, thymosin alpha 1), supporting the notion that the enzyme plays a role only in turnover of smaller peptides formed perhaps as a result of endopeptidase cleavage of proteins or polypeptides containing acetylated Met at the N terminus.

Measurement of total opioid peptides in rat brain and pituitary by radioimmunoassay directed at the alpha-N-acetyl derivative

A sensitive assay, which cross-reacts with and is specific for diverse opioid peptides, is described. This is based on the prior acetylation of samples and subsequent radioimmunoassay with an antiserum highly specific for the acetylated NH2 terminus of opioid peptides. The result is a procedure that can be used to investigate multiple forms of opioid peptides in extracts of biological material. The sensitivity of the assay is approximately 15 fmol of beta-endorphin per incubation tube, i.e., approximately 100-fold greater sensitivity than the radioreceptor assay used in our laboratory. The peptide concentration required for 50% displacement of trace ranged from 0.65 nM (beta-endorphin) to 1.6 nM (Met-enkephalin). The assay apparently shows an absolute requirement for a free (or acetylated) NH2 terminus corresponding to either a Leu- or Met-enkephalin sequence. Use of the assay with and without prior acetylation of sample provides a method for estimation of the ratio of acetylated:nonacetylated opioid peptides in crude or fractionated extracts. The procedure is used to investigate the forms of opioid peptide found in rat brain and pituitary.

Identification of gastrin releasing peptide-related substances in guinea pig and rat brain

Rat and guinea pig brain extracts were examined for the occurrence of gastrin-releasing peptide (GRP)-like substances by sequence specific radioimmunoassays interfaced with gel filtration and reversed phase high performance liquid chromatography (RP-HPLC). Tryptic digestion of the immunoreactive peptides followed by RP-HPLC was used to further characterize GRP-related peptides in brain. Using these analytical techniques it was found that guinea pig brain extracts contained a peptide with characteristics identical to authentic GRP (27 amino acid residues long). A carboxyterminal fragment with the characteristics of GRP(18-27) as well as a respective aminoterminal fragment with the characteristics of GRP(1-16) were also present in guinea pig brain extracts. The GRP(18-27) seems to correspond to the bombes in related material that has been described previously in mammalian brain extracts. Rat brain extracts also contained a peptide with the characteristics of GRP(18-27). The corresponding aminoterminal fragment, however, behaved differently on RP-HPLC from authentic GRP(1-16) and it was not recognized by antibodies directed to the aminoterminal tridecapeptide fragment of authentic GRP. Similarly the GRP-like peptide from rat brain did not comigrate on RP-HPLC with authentic GRP and was unreactive to antibodies directed toward the aminoterminus of GRP.

Immunohistochemical distribution of dynorphin B in rat brain: relation to dynorphin A and alpha-neo-endorphin systems

A specific antiserum was prepared against dynorphin B, an endogenous opioid peptide contained in a recently isolated 4,000-dalton dynorphin. The antiserum did not crossreact with dynorphin A, alpha-neo-endorphin, beta-neo-endorphin, dynorphin-(1-8), or [Leu]enkephalin. In immunohistochemical staining experiments on frozen sections through rat brains from normal and colchicine-treated animals, the antiserum labeled the same neuronal fiber systems previously described as containing both dynorphin A and alpha-neo-endorphin immunoreactive material. The alpha-neo-endorphin/dynorphin A immunoreactive perikarya in the hypothalamic magnocellular nuclei also were labeled by the dynorphin B antiserum. In addition, the dynorphin B antiserum revealed groups of immunoreactive neuronal cell bodies in several other hypothalamic and extrahypothalamic areas, including brain-stem, midbrain, central nucleus of amygdala, and in the dorsomedial, lateral, and anterior nuclei of hypothalamus. These perikarya had not been detected in previous studies that used dynorphin A and alpha-neo-endorphin antisera. The findings are in agreement with recent studies demonstrating a common precursor for dynorphin A, dynorphin B, and alpha-neo-endorphin. The apparently wider distribution of dynorphin B immunoreactive cell bodies compared to alpha-neo-endorphin/dynorphin A immunoreactive perikarya may be a reflection of differential processing of the precursor in different brain regions.

Immunoreactive dynorphin-(1-8) and corticotropin- releasing factor in subpopulation of hypothalamic neurons

Immunoreactive corticotropin-releasing factor (CRF) and dynorphin-(I-8) were visualized in rat hypothalamus by immunohistofluorescence with specific antibodies. In brains from colchicine-treated, adrenalectomized rats, neuronal perikarya with immunoreactive CRF were observed in the paraventricular nucleus of the hypothalamus. The CRF occurred together with the dynorphin-(1-8). However, the CRF immunoreactivity occurred only in a subpopulation of the dynorphin-(1-8) immunoreactive cells. These findings suggest that there may be a functional interrelationship of CRF with dynorphin-related opioid peptides and provide further evidence that neurons may contain more than one bioactive substance.

Naloxone increases vasopressin secretion from the neurointermediate lobe of the hypophysis of the rat: search for the endogenous agonist

Naloxone increases the electrically induced vasopressin release from rat pituitary neurointermediate lobes under appropriate stimulation conditions. In order to examine a possible role of hypophyseal opioid peptides we studied in vitro the effect of opioid peptides and of naloxone on the electrically induced vasopressin release from the rat neurointermediate lobe or isolated neural lobe of the hypophysis. (D-Ala2,D-Leu5)-enkephalin (5 microM), dynorphin-(1-13) (Dyn; 0.2 microM), beta-endorphin (beta-End; 0.02 and 0.2 microM) and also naloxone (1 or 10 microM) increased the evoked vasopressin release from the neurointermediate lobe, but in higher concentrations (2 microM) Dyn or beta-End had no effect. After removal of the intermediate lobe, beta-End 2 microM inhibited, while naloxone 10 microM did not change the evoked vasopressin release from the isolated neural lobe. These results demonstrate that hypophyseal opioid peptides can influence vasopressin release in several ways and suggest that endogenous opioids predominantly provide inhibitory influences which depend on the presence of the intermediate lobe.

Differential effects of acute and chronic ethanol treatment on particular opioid peptide systems in discrete regions of rat brain and pituitary

Acute ethanol treatment induced a significant increase in the tissue levels of immunoreactive (ir-) Met-enkephalin in hypothalamus, striatum and midbrain, but not in hippocampus. Levels of ir-dynorphin, ir-alpha-neo-endorphin and ir-beta-endorphin were not found to be significantly altered in brain and pituitary. Chronic ethanol treatment (by the use of ethanol liquid diet) resulted in a more than 50% decrease of the tissue levels of ir-dynorphin and ir-alpha-neo-endorphin in hypothalamus and hippocampus, while both peptides remained unchanged in midbrain, striatum, adenohypophysis and neurointermediate pituitary. In contrast, ir-met-enkephalin was decreased in striatum and hypothalamus, but unaffected in midbrain and hippocampus. Levels or ir-beta-endorphin remained unchanged in the brain and in the pituitary. However, the de novo biosynthesis of beta-endorphin and its prohormones beta-lipotropin and pro-opiomelanocortin was increased in the intermediate pituitary and to an even more pronounced degree, in the adenohypophysis, after chronic treatment of rats with ethanol liquid diet, nevertheless, the amounts of opiate-active beta-endorphin were found to be reduced in both lobes of the pituitary: In the adenohypophysis, this was due to a retardation of the enzymatic processing of beta-endorphin from its precursor beta-lipotropin, while in the intermediate pituitary the alpha-N-acetylation of beta-endorphin to opiate-inactive alpha-N-acetyl-beta-endorphin was stimulated. In conclusion, acute and chronic ethanol treatment caused selective alterations on different opioid peptide systems within distinct areas of the rat brain and pituitary.

Immunohistochemical localization of dynorphin (1-8) in hypothalamic magnocellular neurons: evidence for absence of proenkephalin

Dynorphin(1-8) immunoreactivity was visualized by immunohistofluorescence in hypothalamic magnocellular neurons of the rat. No immunoreactive met-enkephalin-Arg6-Gly7-Leu8, a fragment of the adrenal medulla pro-enkephalin molecule, was detected in magnocellular neurons. However, a strong met-enkephalin-Arg6-Gly7-Leu8-like immunostaining was seen in other regions of the brain. These results suggest that in magnocellular neurons dynorphin(1-8) exists independently from pro-enkephalin and therefore the magnocellular neurons represent a third opioid peptide neuronal system in brain. These observations, however, do not rule out a coexistence of proenkephalin and dynorphin-related peptides in other regions of the brain.